1. Field of the Invention
The present invention relates to analyzing the chemical nature of materials. More particularly, the present invention relates to sub-micron analysis of chemical properties of a sample material at a particular location of interest by decomposing, desorbing or ablating a small portion of the sample material and transferring the small portion to a chemical analyzer.
2. Background of the Invention
A conventional method for imaging the chemical nature of polymeric systems is imaging Secondary Ion Mass Spectroscopy (SIMS). In imaging SIMS, the surface of a sample is bombarded by a beam of ions (usually argon) that is rastered over the surface. The ions cause material on the surface of the sample to be ejected and ionized. These secondary ions are swept into a mass spectrometer for analysis. SIMS is a very expensive technique that is not easily applicable to insulating samples such as polymers. This is because a charge that builds on the surface of insulating polymer samples deflects the incident ion beam. Although this can be overcome in some cases by bathing the insulating polymer sample with electrons, a great deal of expertise is required to obtain satisfactory results. A further limitation of SIMS is that the sample must be analyzed under high vacuum. It would be desirable in many cases to analyze samples at or above atmospheric pressure or submerged in a substance, for example water.
Another problem with SIMS is that is a continuously destructive imaging technique. As described above, the bombardment of the material by the ion beam causes the surface material to be ejected, thereby destroying the surface. It would be advantageous to have an imaging system which can image the topology and thermal properties of the material without destroying the surface. It is also desirable to be able to study the material after any damage is done as a result of desorption or pyrolysis. Neither kind of study can be performed using conventional SIMS techniques.
The present invention allows chemical studies to be performed on the surface and sub-surface of a material. An image of a sample material is created using any conventional sample imaging technique. Using the image, an area of the sample on which to perform analysis is determined. An activation device is positioned at the selected area of interest. The activation device is activated to cause a portion of the sample to be emitted. The emitted portion of the sample is collected and analyzed to determine its chemical properties. The present invention can be used below, at or above atmospheric pressure or submerged in a substance, for example, water.
In a preferred embodiment of the present invention, the activation device is a highly miniaturized resistive probe as described below. In the preferred embodiment, an image of the sample is created using the probe. Using the resulting image, the probe is positioned at a desired location on the surface. Using a selected heating mode, the probe is heated to cause a portion of the sample to decompose or desorb into a gaseous form. The evolved gas is swept into a heated capillary tube, which is positioned close to the probe. The heated capillary tube is connected to a chemical analyzer, which analyzes the evolved gases. The area from which the material was decomposed or desorbed can further be rescanned to assess the volume ablated. The process is then repeated for another selected area.
The process can be placed under computer control. Using a computer the selected area can be scanned. Further, either an operator or the computer can select areas for analysis.
A first object of the present invention is to provide sub-micron imaging and chemical analysis over a wide-variety of atmospheric pressures, including at or above atmospheric pressure, under a vacuum, and submerged under a substance, for example, water.
Another object of the present invention is to image a sample topology and thermal properties in a non-destructive manner, in addition to obtaining information using pyrolysis and desorption.
Another object of the present invention is to reduce the problems associated with imaging insulators such as polymers.
Another object of the present invention is to provide precise temperature control to increase the resolution of chemical species analysis.
Another object of the present invention is to reduce the cost of conventional sub-micron imaging.
These and other objects of the present invention are described in greater detail in the detailed description of the invention, the appended drawings and the attached claims.